1. Field of the Invention
This invention relates to electronic timepiece and more particularly to an extrememly thin digital electronic timepiece comprising an electrooptical display element composed of an electrochromic display element such as a liquid crystal element, etc.
2. Description of the Prior Art
Most of conventional electronic timepiece have adapted a module construction in which main constitutional members of the electronic timepiece, i.e., a display device, housing, circuit substrate and base plate are superimposed one upon the other and secured together by means of screws. Most of the circuit substrate may be formed of ceramics or glass mixed epoxy resin. On the circuit substrate are mounted a semi-conductor integrated circuit chip, time reference oscillator, condenser and any other electronic parts.
The housing and base plate are molded in thermo-plastic resin such as polyacetal resin and polybutylene telephthalate resin. These constitutional members are superimposed one upon the other in the order such that the display device is located at the uppermost surface and then the housing, circuit substrate and base plate are located in the order as mentioned. That is, the circuit substrate is sandwiched between the housing and the base plate.
The conventional electronic timepiece constructed as above described has been encountered with the following drawbacks.
(1) The use of ceramics or glass mixed epoxy resin makes dimensions of the timepiece unstable and resistance to shocks low and is particularly unsuitable for making the timepiece thin in thickness. PA0 (2) The circuit substrate formed of glass mixed epoxy resin is of a single body or sheet-shaped one so that it is difficult to manufacture it by a continuous automatic process. PA0 (3) The housing and base plate are formed of synthetic resin and hence can easily be molded, but is poor in strength. As a result, in order to guarantee a resistance to shock it is necessary to make these members considerably thick in thickness. PA0 (4) Since the housing, circuit substrate and base plate are not satisfactorily high in strength, it is difficult to provide a timepiece module having a high regidity by a combination of these members and to make it thin in thickness.
As a result, it is eagerly desired to provide an electronic timepiece which is so constructed as to eliminate the above mentioned drawbacks which have been encountered with the prior art techniques.